The present invention generally relates to the counter-balancing of a reciprocating piston, internal combustion engine to eliminate imbalance thereof and, more particularly, is concerned with an inline counterbalance weight system for a single cylinder engine which eliminates vibratory imbalance due to piston reciprocation and crankshaft rotation without introducing rocking couple imbalance about the mounting base of the engine.
A limiting characteristic of a small single cylinder internal combustion engine is the high vibration level created by the engine. Vibrations are inherently generated in such engine, originating from the centerline of its rotation crankshaft and oriented along the line of reciprocating movement of its piston passing through the crankshaft centerline. The vibratory force generated by the engine and transmitted to the operating machine to which the engine is attached and to which it supplies rotary driving power is annoying to the user and can be harmful to the reliability of the machine and shorten its operating life.
Different balancing arrangements are known in the prior art for mounting on a single cylinder engine to provide a balancing force to oppose the vibratory force and thereby substantially reduce or eliminate vibrations incident to the reciprocation of the piston and motion of the crankshaft and other connecting parts of the engine. The approach of one balancing arrangement for a single cylinder engine, such as disclosed in U.S. Pat. No. 2,407,102 to Ryder, is to eccentrically mount a balancing weight on an auxiliary shaft disposed on the engine parallel to its crankshaft and driven from the crankshaft to rotate in an opposite direction. The balancing weight is located intermediate a pair of weights eccentrically mounted on the crankshaft and the auxiliary shaft is displaced laterally from the line of reciprocation of the piston.
In another balancing arrangement for a single cylinder engine, a pair of balancing weights are offset in the same direction from the line of reciprocation of the piston and in opposite directions from the crankshaft. The balancing weights are eccentrically mounted on the engine for rotation about axes which extend generally parallel to the crankshaft. Their direction of rotation is opposite to that of a pair of eccentric weights mounted on the crankshaft. While these balancing arrangements substantially counterbalance and eliminate the vibratory force emanating from the centerline of the crankshaft along the line of reciprocation of the piston, they introduce an undesirable rocking couple about the mounting base of the engine.
Consequently, a need still exists for a balancing arrangement for a single cylinder engine which will eliminate vibratory imbalance due to piston reciprocation and crankshaft and connecting rod rotational motion without substituting other imbalance forces in its place.